This section provides background information related to the present disclosure which is not necessarily prior art.
As an infrastructure of telecommunication networks, optical networks have witnessed quick development and become a core of future Wide Area Networks and Metropolitan Area Networks. Of all optical networks, Wavelength Division Multiplexing (WDM) optical networks attract extensive attention. The emergence of Wavelength Routing Switches (WRSs) and Photonic Cross Connectors (PXCs) enable networks to perform data switching in the optical domain. Routing and Wavelength Assignment (RWA) refers to computing routes and assigning wavelengths for connection requests. RWA is one of the core technologies for a WDM optical network. When there arises an optical service setup request, RWA computes how to select a route from the source node to the destination node of the traffic from the physical topology structure of the network and assigns a wavelength for the links that the route passes. Through RWA, an appropriate optical channel is selected and a wavelength is reasonably assigned to the optical channel, so that the finite resources are fully utilized to provide the highest possible communication capacity.
In a WDM optical network, an optical channel is determined by the optical switching nodes and optical links that the channel passes and by the wavelength assigned to each optical link that the channel passes. In an all-optical group without wavelength conversion capabilities, an optical channel must be set up by using a common wavelength for all the links of the route. This is called wavelength continuity constraint. Due to this constraint, optical path computation cannot be simply divided into route selection and wavelength assignment. For instance, such a case may exist: every link of a route has available wavelengths for use, but there is no common wavelength for all the links of the route. In this case, an optical switch with extra optical/electrical conversion and wavelength conversion capabilities may be used to ease the wavelength continuity constraint, and divide an optical channel into several sub-connections with different wavelengths to form an optical path.
An Automatic Switched Optical Network (ASON) is a new-generation optical network that integrates switching and transmission functions. It is a transport network based on dynamic and automatic switching. In an ASON, users dynamically initiate service requests, a node automatically computes and selects routes, and a connection is established, restored and removed through signaling control. Therefore, a very good way for establishment of a connection is to combine an ASON with the RWA of a WDM optical network so that the ASON selects wavelengths and routes for the WDM optical network.
A conventional WDM network is a static point-to-point network. The emergence of intelligent optical switching technologies such as the Optical Cross-Connect (OXC) technology makes a dynamic WDM network possible. Operators can provide end-to-end wavelength switching and configuration without redesigning their networks. Therefore, operators can deploy new services and dynamically add or modify network services.
A mode, that is, separately performing route selection and wavelength assignment, may solve the influence of wavelength continuity constraint and cross-connect restrictions on routing and wavelength assignment. The method adopted by this mode is as follows: the system selects a route without considering wavelength resources and then detects which wavelengths are available along the route, and if no wavelengths are available along the selected route, the system reselects another route and detects which wavelengths are available along the reselected route.
It is better to consider both route selection and wavelength assignment simultaneously, but how to release the information between traffic engineering (TE) links is an issue.